Error budget and uncertainty analysis of portable machines by mixed experimental and virtual techniques

- Main error sources of using portable machines are studied.
- Error-budget of a particular portable machine is performed.
- Error values are obtained from experimentation and a virtual machine model.
- Uncertainty in the use of the studied portable machines is below 0.06 mm.
- Main areas for error improvement are identified.

This paper analyzes the error sources of portable machines, which can move along large parts to perform machining operations and defines a mixed virtual-experimental model to quantify such errors. The method combines three different aspects of particular relevance in portable machines: a process force and machine stiffness model, a geometric error model and a machine and work piece inter-referencing error model. The combination of these models helps to control and define the effects of different errors in the virtual mobile machine, before a real prototype is built. An application to a particular portable machine is presented where error values are either simulated or experimentally obtained from a conventional three-axis milling machine where typical strategies of mobile machines are implemented and tested. The research shows that portable machines can be a solution for automatic and unattended machining operations with accuracy requirements below 0.1 mm.